Many crucial immune functions are mediated by T cell receptors (TCRs), which comprise α and β subunits that together bind to a complex consisting of an antigenic peptide and major histocompatibility complex (MHC) molecules. It is believed that several important diseases arise from aberrant T cell function: For example, cancers are thought to arise from a failure of immune surveillance, that is, the T cell function of detecting and destroying clones of transformed cells before they grow into tumors; and autoimmune diseases are thought to arise from an over active or aberrant response of T cells to self antigens, Abbas et al, Cellular and Molecular Immunology, Fourth Edition (W. B. Saunders Company, 2000). Consequently, there has been interest both in identifying and tracking antigen-specific T cells and in harnessing T cell functions in several therapeutic approaches for the treatment both cancer and autoimmune diseases, e.g. Molloy et al, Current Opinion in Pharmacology, 5: 438-443 (2005); Morgan et al, Science, 314: 126-129 (2006); Turcotte and Rosenberg, Adv. Surg., 45: 341-360 (2011). Several challenges are posed by these interests: Current techniques for identifying and tracking antigen-specific T cells, especially on a large scale, are difficult and expensive, and likewise, current techniques for identifying and isolating paired TCRα and TCRβ subunits that form a functional receptor are difficult and expensive. In regard to detecting antigen-specific T cells, the use of direct multimer staining requires laborious development of specific HLA-restricted reagents, and other assays, such as ELISPOT, intracellular cytokine staining, and proliferation assays, enumerate antigen-specific T cells based on detection of activation following stimulation of the T cells in vitro with antigen, e.g. Gratama et al, Cytometry A, 73A: 971-974 (2008). In regard to isolating functional pairs of TCR chains, typically a T cell of interest is identified and clonally expanded to enable isolation and analysis of nucleic acids encoding each subunit. Even for a common disease antigen, such as MART-1 in melanoma, the process of single cell analysis, cloning and receptor isolation must be repeated for each patient.
Recently, diagnostic and prognostic applications have been proposed that use large-scale DNA sequencing as the per-base cost of DNA sequencing has dropped and sequencing techniques have become more convenient, e.g. Welch et al, Hematology Am. Soc. Hematol. Educ. Program, 2011: 30-35; Cronin et al, Biomark Med., 5: 293-305 (2011); Palomaki et al, Genetics in Medicine (online publication 2 Feb. 2012). In particular, profiles of nucleic acids encoding immune molecules, such as T cell or B cell receptors, or their components, contain a wealth of information on the state of health or disease of an organism, so that diagnostic and prognostic indicators based on the use of such profiles are being developed for a wide variety of conditions, Faham and Willis, U.S. patent publication 2010/0151471; Freeman et al, Genome Research, 19: 1817-1824 (2009); Boyd et al, Sci. Transl. Med., 1(12): 12ra23 (2009); He et al, Oncotarget (Mar. 8, 2011). Current sequence-based profiles of immune repertoires consist of nucleic acids encoding only single receptor chains; thus, potentially useful information from correctly paired TCRα and TCRβ chains chains is not available.
In view of the above, it would be highly useful for cancer, infectious disease and autoimmune disease treatment if there were available convenient methods for determining functional immune receptors from nucleic acids encoding subunits that have been separately extracted and sequenced.